1. Field of the Invention
The present invention relates to an incremental offset measuring instrument for accurately determining dimensions of objects, thereby reducing product loss during manufacturing processes.
2. Description of the Prior Art
Please refer to FIG. 1. FIG. 1 is a typical view of a prior art guide ring 10 and a wafer 15 to-be-polished. As shown in FIG. 1, the wafer 15 is subject to a typical polishing process in order to remove a layer of material from the wafer surface. During the polishing process, the wafer 15 is protected and restrained by the guide ring 10. In an ideal case, the diameter of the wafer 15 is equal to the inner diameter of the guide ring 10 so that the water 15 can be fittingly placed in the guide ring 10. It is known that large space between the wafer peripheral and the guide ring 10 can cause sever collision or even drop off of the wafer 15 during the polishing process.
However, a very small space between the wafer peripheral and the guide ring 10 and collision are usually inevitable during mass production. Frequent collision of wafers results in incremental offset of the inner diameter of the guide ring 10. A step cross section of the guide ring 10 is observed due to incremental offset of the inner diameter of the guide ring 10. Referring to FIG. 2, the cross section of the guide ring 10 without a step cross section is shown. Referring to FIG. 3, the cross section of the guide ring 10a with a step cross section is shown. When the step difference 12 exceeds a predetermined value, the wafer 15 is subject to sliding out of the guide ring 10 during the polishing process and may be broken. Consequently, it is an important task of measuring friction loss of the guide ring 10 and the step difference 12.
Referring to FIG. 4 and FIG. 5, a typical way to the measurement of the step difference 12 of the guide ring 10 is according to experience of an operator. When measuring, the operator uses his nail of a finger as a measuring tool, thereby determining if the guide ring 10 can be used in the next polishing process or not. However, the prior art method is not accurate and cannot obtain quantified data that can be used as a basis for effective management of wafer polishing process.
It is therefore a primary object of the present invention to provide an incremental offset or step difference measuring instrument for accurately measuring the step difference of a guide ring.
Another object of the present invention is to provide an incremental offset or step difference measuring instrument for accurately measuring the step difference of a guide ring and obtaining quantified data that are used as a basis of a wafer polishing management standard.
Still another object of the present invention is to provide an incremental offset or step difference measuring instrument for accurately measuring the step difference of a guide ring thereby determining the lifetime of the guide ring and decreasing the cost of production.
Still another object of the present invention is to provide an incremental offset or step difference measuring instrument for accurately measuring the step difference of a guide ring thereby avoiding a dropped wafer from damaging pricey semiconductor equipment.
According to the claimed invention, an incremental offset measuring instrument is provided. The incremental offset measuring instrument includes a main base; a specimen seat mounted on the main base for resting a specimen; a measuring tool assembly for measuring the specimen; and a movable assembly mounted on the main base, wherein the movable assembly carries the measuring tool assembly, thereby achieving the goal of measuring the specimen.
It is to be understood that both the forgoing general description and the following detailed description are exemplary, and are intended to provide further explanation of the invention as claimed. Other advantages and features of the invention will be apparent from the following description, drawings and claims.